A positive electrode and a negative electrode for a lithium secondary battery are charged and discharged through absorption and desorption of lithium. However, the absorption and desorption are not completely reversible reactions. A large ratio of the lithium that has been absorbed in the negative electrode during initial charge may fail to be desorbed from the negative electrode during discharge. The difference in capacity between during charge and during discharge caused by the lithium that cannot be desorbed is called an irreversible capacity. If the irreversible capacity at the time of the initial charge is large, the use efficiency of the lithium stored in the positive electrode is reduced. This hinders the improvement of charge/discharge capacity.
To solve the foregoing problem, a method of allowing lithium to be absorbed and stored in a negative electrode active material layer before assembly of a lithium secondary battery so as to reduce the irreversible capacity is known (for example, JP 2004-303597 A). Particularly, a method of performing vapor deposition of a lithium-containing material and thereby allowing lithium to be absorbed through the surface of a negative electrode active material layer is excellent in uniformity and continuous processing, which has therefore been studied widely.